A Synergistic Effect of Apomorphine on Sildenafil Induced Penile Erection in Conscious Rabbits

Park, Jae Young; Son, Hwan cheol; Paick, Jae Seung

Abstract

PURPOSE: The aim of this study was to demonstrate that the combined systemic administration of apomorphine (APO) and sildenafil have a synergistic effect on the erection in conscious rabbits.
MATERIALS AND METHODS
The erections of the male New Zealand White rabbits (2-3kg, n=12) were assessed by measuring the length of the uncovered penile mucosa (LUPM) and duration of the erection, both before and after the intravenous administration of agents. After the injection of APO (0, 0.05, 0.1, 0.4mg/kg), sildenafil was administered intravenously in a dose-response manner (0.5, 1, 5mg/kg), followed by measurements for 0-120 minutes. In additional experiments, the effect of increasing the dosages of sildenafil, combined with APO, on blood pressure were evaluated.
RESULTS
The intravenous administration of sildenafil caused a concentration dependent increase in the LUPM. There was a statistically significant increase in the LUPM with the administration of APO compared with no administration. The dosages of sildenafil and APO showing the greatest efficacy of sildenafil potentiation were 1mg/kg and 0.1 mg/kg, respectively. The intravenous administration of APO at a dose of 0.1mg/kg was more effective than those of 0.05 and 0.4mg/kg, with dosages of sildenafil of 0.5 and 1mg/kg. There was no additional increase in the duration of erection on the administration of APO. The intravenous administration of sildenafil caused a concentration dependent decrease in blood pressure, but there was no additional decrease on administration of the APO.
CONCLUSIONS
We have shown that apomorphine elicits a stronger response on the erection induced by sildenafil in conscious rabbits, with no additional decrease in blood pressure.